1. Technical Field
The present invention relates to a portable wireless apparatus and, more particularly, to a portable wireless apparatus where at least two housings are foldably connected to each other.
2. Description of Related Art
Portable wireless apparatus, such as a portable telephone, have employed an antenna diversity technique that use a plurality of antennas and that selectively or synthetically enhances the quality of signals sent therefrom and received thereat. A portable wireless apparatus has hitherto been known, which performs antenna diversity using what is called a whip antenna externally extended from a housing thereof, and also using a built-in antenna, for example, an inverted-F antenna incorporated in the housing thereof. Recently, another portable wireless apparatus has been known, which effects antenna diversity using a plurality of antennas incorporated in a housing thereof (see, for example, Japanese Patent No. 3,112,464 (Pages 1 to 4 and FIG. 3 or JP-A-2002-027860 (Pages 2 and 3 and FIG. 3)).
According to a technique disclosed in Japanese Patent No. 3112464, there have been strong demands for not only the miniaturization of the built-in type antenna of the portable wireless apparatus but that of a non-built-in type antenna thereof. Thus, the portable wireless apparatus is often configured so that a high frequency current distributing in a grounding circuit provided on a board or distributing on a conductive part of a housing is utilized, rather than a high frequency current distributing on an antenna element itself when excited, as a main radiation source. In such a case, even when diversity is effected using a plurality of antennas, it is difficult to fully obtain advantages of the diversity in an occasion where the grounding circuit on the board or the conductive part of the housing, on which the high frequency current distributes, is shared by the antennas.
According to the above-mentioned related art, diversity is achieved by using a first antenna and a second antenna which are respectively provided two housings turnably connected to each other. A main radiation source of radiowaves (the conductive part of one of the housings or the grounding circuit on one of the built-in boards), which is used when the first antenna is excited, is separated from a main radiation source of radio waves (the conductive part of the other housing or the grounding circuit on the other built-inboard), which is used when the second antenna is excited. The correlation in radiation characteristics between the first antenna and the second the antenna is weakened, so that advantages of antenna diversity can be obtained.
According to technique disclosed in JP-A-2002-027860, in a portable wireless apparatus performing antenna diversity using a main antenna and an auxiliary antenna, a linear antenna extending perpendicularly to a board surface is folded to be parallel with the longitudinal direction of the board and is formed as the auxiliary antenna. Thus, the auxiliary antenna is formed into an inverted-L shape so that the auxiliary antenna can compensate the degradation in sensitivity of the main antenna due to change in orientation or posture thereof.